Abstract An archaeomagnetic intensity study was conducted on nineteenth-century firebricks manufactured in Scotland and used in an iron foundry in Melbourne, Australia, between 1842 and 1864 CE. Archaeointensity results obtained from bricks with a single component of magnetization gave values of 61.45 ± 0.89 and 61.92 ± 6.84 μT. These values are in agreement with historical absolute intensity measurements taken at the Melbourne geomagnetic observatory between 1858 and 1863 CE (61.17 ± 0.078 μT) and with the gufm1 model based on mariners’ data. A high-temperature vector component, presumably acquired at the time of manufacture in Scotland, was isolated in certain firebricks and an archaeointensity of 48.3 ± 8.39 μT was obtained, which is consistent with the gufm1 model for Scotland at this time (48.79 μT). The dual archaeointensity record of the firebricks supports their geographical provenance, highlighting the potential for archaeointensity data to be used in archaeological artefact-sourcing studies, whilst anomalously high intensities recorded in one of the bricks highlight potential contamination issues from non-Earth magnetic fields in archaeometallurgical contexts. The new Melbourne archaeointensity data are the most precisely dated archaeomagnetic data produced so far for Australia.

Average orogenic strain rates may be calculated when it is possible to date mica cleavage or syndeformational veins and estimate finite strain. Deformation of accretionary-style thrust sheets in the western Lachlan Orogen occurred by chevron folding and faulting over an eastward propagating décollement. Based on 40 Ar/ 39 Ar dates of white micas, which grew below the closure temperature, this deformation started ca. 457 Ma in the west and ended ca. 378 Ma in the east, with apparent “pulses” of deformation ca. 440, 420, and 388 Ma. The 40 Ar/ 39 Ar data from thrust sheets in the Bendigo structural zone show that deformation progressed from early buckle folding, which started at 457–455 Ma, through to chevron fold lock-up and thrusting at 441–439 Ma. Based on retrodeformation, the total average strain for this thrust sheet is −0.67, such that the bulk shortening across the thrust sheet is 67%. This amount of strain accumulated over a duration of ∼16 m.y. gives a minimum strain rate of 1.3 × 10 −15 s −1 and a maximum strain rate of 5.0 × 10 −15 s −1 , based on fan thickness considerations. The total shortening is between ∼310 km and ∼800 km, which gives a décollement displacement rate between ∼19 mm yr −1 (minimum) and ∼50 mm yr −1 (maximum). If deformation occurred in pulses ca. 457–455 and ca. 441–439 Ma, then the calculated strain rate would be on the order of 1 × 10 −14 s −1 . These strain rates are similar to convergence rates in western Pacific backarc basins and shortening rates in accretionary prisms and turbidite-dominated thrust systems as in Taiwan.